igneous
Granite
Phaneritic intrusive igneous rock
Hardness: 6-7 Mohs; Color: Pinkish-red, grey, black mottled pattern; Luster: Dull (weathered/water-worn); Crystal Structure: Coarse-grained phaneritic; Cleavage: None (grains have individual cleavage)
- Hardness
- 6-7 Mohs
- Color
- Pinkish-red, grey, black mottled pattern
- Luster
- Dull (weathered/water-worn)
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Physical properties
Hardness: 6-7 Mohs; Color: Pinkish-red, grey, black mottled pattern; Luster: Dull (weathered/water-worn); Crystal Structure: Coarse-grained phaneritic; Cleavage: None (grains have individual cleavage)
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. This specimen appears to be a river-worn or glacially-transported pebble, resulting in its rounded shape. Its age typically ranges from hundreds of millions to billions of years.
Uses & applications
Used in construction, monuments, countertops, and as decorative gravel. Small tumbled pieces are common for teaching geology and as landscape stones.
Geological facts
Granite makes up much of the continental crust. The pink color in this specific specimen is due to a high concentration of potassium feldspar (orthoclase).
Field identification & locations
Identify in the field by its 'salt and pepper' or mottled appearance with visible interlocking crystals of quartz, feldspar, and mica. Found globally in mountainous regions or glacial till.
